Abstract
Cytochrome c is electroactive at TiO2 modified SnO2 electrodes, displaying quasi-reversible behavior. When water was replaced by glycerol (95%), E°′ increased slightly from 254 to 261 mV (NHE). Resonance Raman and visible spectroscopic data indicated that the heme environment was unchanged in glycerol. The thermodynamics of reduction were significantly changed, with ΔH°′rc decreasing from -35.6 to -47.7 kJ mol-1 and ΔS°′rc from -35.2 to -76.8 J K-1 mol-1. The large decrease in ΔH°′rc is a result of exclusion of water molecules from the heme environment, while the decrease in ΔS°′rc can be attributed to the reduced conformational flexibility of the protein in glycerol. The activation energy associated with electron transfer is significantly increased from 5.7 kJ mol-1 in aqueous buffer to 44.2 kJ mol-1 in glycerol. These results demonstrate that a relatively polar solvent can significantly affect the redox properties of cytochrome c.
Original language | English |
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Pages (from-to) | 1282-1286 |
Number of pages | 5 |
Journal | Langmuir |
Volume | 19 |
Issue number | 4 |
DOIs | |
Publication status | Published - 18 Feb 2003 |